Annular Stratified Flow Model for Inclined Pipes
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Solution Overview
Problem
Current models for annular stratified flow in pipeline transport of gas-condensate fluids fail to accurately predict pressure drop and account for asymmetry in fluid flow, particularly at low liquid loading and non-vertical pipe orientations, due to oversimplification of liquid distribution and lack of consideration for gravity effects on phase separation.
Innovation Solution
A new fluid flow model is developed that determines liquid and gas velocity distributions and film roughness by balancing gravity forces and turbulent stresses, allowing for asymmetric flow distribution and accounting for three-phase effects by modeling the liquid film and layer as homogeneous mixtures, which improves pressure drop predictions and captures the effects of pipe inclination and liquid viscosity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If current stratified flow models are used, then model simplicity is maintained, but pressure drop prediction accuracy deteriorates
Solution Approach 1:
The flow is segmented into distinct regions: a thin annular liquid film near the pipe wall, a bulk liquid region, and a gas core. Each region is modeled separately with appropriate velocity distributions and stress balances, allowing accurate prediction of pressure drop while maintaining manageable model complexity through regional decomposition
Solution Approach 2:
Different velocity distribution profiles are applied to different regions: parabolic profile for the thin film, plug flow for the bulk liquid, and turbulent profile for the gas core. This local differentiation captures the physical reality of annular stratified flow while improving prediction accuracy without requiring a completely complex model
2Adaptability or versatility
If vertical flow assumptions are applied, then axisymmetric flow distribution is assumed, but accuracy for inclined and horizontal flows deteriorates
Solution Approach 1:
The model explicitly accounts for asymmetric flow distribution in inclined and horizontal pipes by introducing a gravity angle parameter. The liquid film thickness and velocity distribution are calculated as functions of pipe inclination, capturing the asymmetric accumulation of liquid at the lower portion of the pipe while maintaining the core annular stratified flow structure
Solution Approach 2:
The model uses parameter changes to adapt to different flow orientations. By varying the gravity angle parameter from 0° (vertical) to 90° (horizontal), the model continuously adjusts the liquid distribution and velocity profiles to match the physical behavior at each orientation, enabling versatility across different pipe configurations
3Device complexity
If liquids are assumed to be perfectly mixed, then model complexity is reduced, but prediction accuracy for three-phase flow deteriorates
Solution Approach 1:
The three-phase flow is segmented into distinct liquid and gas regions with separate velocity distributions. The liquid phase is further divided into film and bulk regions, each with its own flow characteristics. This segmentation allows accurate representation of phase separation effects while maintaining model tractability through region-specific formulations
Solution Approach 2:
The model introduces an intermediary approach for three-phase flow by using effective liquid properties that represent the combined behavior of multiple liquid phases. Rather than tracking each phase separately throughout the domain, the model uses mixture models in the bulk region while maintaining distinct phase behavior in the thin film, balancing complexity and accuracy
4Device complexity
If thin film roughness is neglected, then model simplicity is maintained, but frictional pressure gradient prediction deteriorates
Solution Approach 1:
The model incorporates film roughness as a variable parameter that changes with liquid flow rate and pipe inclination. Rather than assuming constant or negligible roughness, the model calculates effective roughness based on the thin film characteristics, capturing its increasing influence at low liquid loading while maintaining model simplicity through parameter-based representation
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The model effectively predicts pressure drop and liquid distribution in annular stratified flows, especially at low liquid loading, and provides improved accuracy for inclined and horizontal flows by accounting for gravity-driven phase separation and film roughness, reducing errors and enhancing predictive capabilities.
Implementation Method 1
determining a film roughness between the liquid and gas components at least in part by balancing gravity forces and turbulent stresses
Implementation Method 2
determining a film roughness between the liquid and gas components at least in part by balancing gravity forces and turbulent stresses
Data Source
AI summary
Methods and systems for modelling annular multiphase fluid flows in a structure are disclosed. In one example, a method is disclosed that includes determining a liquid velocity distribution for a liquid component the multiphase fluid flow; determining a gas velocity distribution for a gas component of the multiphase fluid flow; determining a film roughness between the liquid and gas components at least in part by balancing gravity forces and turbulent stresses so that asymmetry in the fluid flow increases as a deviation of the structure from a first direction; and generating a fluid flow model based in part on the liquid and gas velocity distributions and the film roughness.